Cluster Core Controlled Reactions of Substitution of Terminal Bromide Ligands by Triphenylphosphine in Octahedral Rhenium Chalcobromide Complexes

Reactions of rhenium chalcobromides Cs4[{Re6(μ3-S)8}Br6]·2H2O, Cs3[{Re6(μ3-Se)8}Br6]·2H2O,
Cs3[{Re6(μ3-Q)7(μ3-Br)}Br6]·H2O (Q = S, Se), and K2[{Re6(μ3-S)6(μ3-Br)2}Br6] with molten triphenylphosphine
(PPh3) have resulted in a family of novel molecular hybrid inorganic−organic cluster compounds. Six
octahedral rhenium cluster complexes containing PPh3 ligands with general formula [{Re6(μ3-Q)8-n(μ3-Br)n}(PPh3)4-nBrn+2] (Q = S, n = 0, 1, 2; Q = Se, n = 0, 1) have been synthesized and characterized by
X-ray single-crystal diffraction and elemental analyses, 31P{1H} NMR, luminescent measurements, and
quantum-chemical calculations. It was found that the number of terminal PPh3 ligands in the complexes is
controlled by the composition and consequently by the charge of the cluster core {Re6Q8-nBrn}n+2. In crystal
structures of the complexes with mixed chalcogen/bromine ligands in the cluster core all positions of a
cube [Q8-nBrn] are ordered and occupied exclusively by Q or Br atoms. Luminescence characteristics of
the compounds trans-[{Re6Q8}(PPh3)4Br2] and fac-[{Re6Se7Br}(PPh3)3Br3] (Q = S, Se) have been
investigated in CH2Cl2 solution and the broad emission spectra in the range of 600−850 nm were observed.